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Abstract: The dependence of water line broadening coefficients on the “good” quantum numbers − angular momentum and symmetry of the upper and lower levels − is analyzed for rotational quantum numbers up to J=50. Trends are investigated separately for P-, Q-, and R-branch transitions for the atmospherically important isotopologue of water. Results are presented which were obtained using two different methods: By averaging the broadening coefficients from HITRAN-2008 for small J values and also by averaging of data calculated using a semi-empirical method for higher J. The resulting air-broadening coefficients allow water vapor spectra with millions of weak lines to be calculated with an accuracy reasonable for many applications, for example estimation of sun radiation with low resolution. Sample results of calculations are presented. [ABSTRACT FROM AUTHOR]

Abstract: Despite the long-term history of extensive studies on water vapor continuum absorption it can hardly be said that an exhaustive consideration has been given to this problem both from experimental and theoretical viewpoints. For instance, deficiency remains concerning the precise data on the absorption coefficient as a function of temperature, especially at reduced temperatures. New experimental data on water vapor continuum absorption in the 800–1250cm−1 spectral region at temperatures from 311 to 363K have become available quite recently . Two advanced variants of the line wing theory – asymptotic and quasistatic – are briefly outlined. The asymptotic line wing theory has been used successfully to describe the absorption coefficient both at elevated temperatures of the Baranov study and at the temperatures of earlier experimental data. Comparison is made with the results obtained from the quasistatic line wing theory. [ABSTRACT FROM AUTHOR]

Abstract: The water vapor line broadening and shifting in the ν 1+ν 2+ν 3 band induced by nitrogen pressure are measured with Bruker IFS 125 HR FTIR spectrometer at the spectral resolution of 0.01cm−1 for the line with upper states angular momentum up to 11. Line contour parameters are calculated using a semi-empirical approach extended by the use of empirical data to determine some fitting model parameters. We use the complete set of high accuracy vibration–rotation dipole transition moments calculated for all possible transitions using wavefunctions determined from variational nuclear motion calculations and an ab initio dipole moment surface. Calculated values of line contour parameters are in a good agreement with observed parameters. [ABSTRACT FROM AUTHOR]

Abstract: This paper addresses the question of errors in retrievals of vertical profiles of ozone from atmospheric spectra caused by assuming that the absorption lines have pure Voigt line shapes. The case of collisionally isolated transitions (no line mixing) is treated by considering only the effects of the speed dependence (SD) of the pressure broadening. The case of O3 retrievals from a sequence of limb transmission spectra is first treated theoretically. The results show that the influence of SD is very small, leading to changes in the residuals and in the retrieved O3 mixing ratios smaller than 1%. These findings are then confirmed by treating a series of spectra recorded by the ACE-FTS instrument. Similar exercises are also made for other observation techniques by treating simulated or measured limb and nadir emission spectra as well as ground-based solar and in-situ laser transmission data. All lead to the general conclusion that SD (and Dicke narrowing) can be neglected in retrievals of ozone amounts from recorded atmospheric spectra. Indeed, the biases caused in the ozone profiles by the use of pure Voigt line shapes still remain significantly smaller than the total error/uncertainty from other sources such as improper line intensities and widths, uncertainty in the instrument function, errors in the pressure and temperature profiles and so forth. [Copyright &y& Elsevier]

Abstract: The hydrogen peroxide () molecule plays an important role in stratospheric ozone chemistry as a reservoir molecule in the cycle. The Superconducting Sub-Millimeter-Wave Limb Emission Sounder (SMILES) instrument in the Japanese Experiment Module (JEM) on the International Space Station monitors using the pure rotational transition at 625.044GHz in the ground vibronic state. Accurate retrievals of abundances rely on a knowledge of pressure broadening effects for this transition, and the required nitrogen () and oxygen () broadening coefficients are measured here for the first time. Values of the pressure broadening coefficients, and are obtained at room temperature, with statistical uncertainties given. The value for air broadening is then derived to be , where the uncertainty includes possible systematic errors. [Copyright &y& Elsevier]

Abstract: Helium broadening coefficients for the R(10) and the P(2) lines in the ν3 band of 13CO2 have been measured over a large range of temperature (70K–300K). Helium pressure shifts for the R(10) line at several temperatures between 100K and 300K have also been determined. These measurements were obtained with a cold Herriott cell, using the collisional cooling technique to reach the lowest temperatures. They provide an extended dataset for the temperature dependence of widths and shifts. This dataset was compared to theoretical He-broadening coefficients combining quantum scattering calculations and the latest potential energy surface for the system He–CO2 from Korona et al. [T. Korona, R. Moszynski, F. Thibault, J.-M. Maunay, B. Bussery-Honvault, J. Boissoles, P.E.S. Wormer, J. Chem. Phys. 115 (2001) 3074–3084]. [Copyright &y& Elsevier]

Abstract: We present new measurements of the line strengths in the third vibrational overtone band in pure HI and its mixtures with Ne, Ar, and Xe, and report results of the Herman–Wallis analysis for this band. Significance of the higher-order terms in the polynomial representation of the dipole moment function is discussed. It is concluded that the spectroscopic data yield the dipole moment function fully described by a cubic polynomial in powers of the reduced displacement from the equilibrium bond length. In the Padé approximant for the dipole moment function, the vicinity of the saddle point near equilibrium also can be accurately fitted with a cubic polynomial. Pressure line broadening and shifting parameters are reported for mixtures of HI with rare gases. [Copyright &y& Elsevier]

We have derived formulations for the pressure derivatives of bulk modulus up to the third order and for higher order Grüneisen parameters using the generalized free volume theory, and the generalized Rydberg equation of state. The properties derived in the present study are directly related to the understanding of thermoelastic properties of solids. The third order Grüneisen parameter (lambda λ) in the limit of infinite pressure has been found to approach a positive finite value for lambda infinity (λ∞) equal to 1/3. This is a result shown to be independent of the value of K-prime infinity, i. e., the pressure derivative of the bulk modulus at infinite pressure. The results based on other equations of state have also been reported and discussed. We find a relationship between λ∞ and pressure derivatives of bulk modulus at infinite pressure which is satisfied by different types of equations of state. [ABSTRACT FROM AUTHOR]

Abstract: Accurate pressure broadened profiles of alkali resonance doublets are needed for modelling of the atmospheres of cool stars and for generating their synthetic spectra in the region 400–900nm. When the usual impact theory of line broadening is used, the profile is simply Lorentzian and the widths and shifts of the lines can be calculated, provided that interaction potentials for the emitter–perturber system are available. However when the lines utterly dominate their region of the spectrum, it becomes important to also accurately represent the profile in the line wings, where the impact theory is no longer valid. The original development of line broadening theory by Baranger in 1958 is reexamined and calculations have been carried out in which it is shown that it is not necessary to invoke the impact approximation. To test the validity of different approximations, results for line widths and shifts are presented for the lithium and sodium resonance lines broadened by helium for 0.1K⩽ T ⩽3000K. [Copyright &y& Elsevier]

Absolute peak absorption cross sections and pressure broadening coefficients have been recorded with sub-Doppler limited instrumental resolution for selected rotational lines in the 202401vibronic band of the formaldehyde Ã1A2−X̃1A1electronic transition. The measured absorption cross sections range between (0.18 ± 0.01) and (10.1 ± 0.08) × 10−19cm2molecule−1and are considerably larger than values from the literature recorded using apparatus where instrumental broadening was significant. However, comparisons with spectral simulations with equivalent resolution from Smith et al. (J. Phys. Chem. A2006, 110, 11645−11653) are in excellent agreement. Pressure broadening was studied for the collision partners CH2O, CO2, N2, O2, Ne, Kr, Ar, and He, and the resulting broadening coefficients were found to be reduced in comparison to equivalent values measured in infrared regions, consistent with the reduced dipole moment of the upper state probed in this work. Cavity-enhanced absorption spectroscopy (CEAS) measurements were undertaken using calibrated low concentration (2.9−4.6 ppmv) samples from a permeation source and demonstrate a noise equivalent absorption of 1.2 × 10−6cm−1Hz−1/2. This implies a minimum detectable formaldehyde concentration with the current system in atmospheric air of 172 ppbv Hz−1/2. [ABSTRACT FROM AUTHOR]

Abstract: A number of satellite instruments are measuring nitric acid, HNO3, in the Earth''s atmosphere. In order to do retrievals of temperature and concentration profiles, the spectral parameters for many thousands of HNO3 transitions must be known. Currently the HITRAN database uses a constant estimated value for the air-broadened half-width of HNO3. To help improve the line shape parameters, complex Robert–Bonamy calculations were made to determine N2-broadened half-widths for some 5000 transitions of HNO3 in the ν 5 band. The intermolecular potential is a sum of electrostatic terms (dipole–quadrupole and quadrupole–quadrupole) and the atom–atom potential expanded to eighth order. The trajectory parameters were adjusted to yield better agreement with measurement. Velocity integrated calculations were made at seven temperatures in order to determine the temperature dependence of the half-widths. The half-width data are compared with available rotation band measurements. The average percent difference between the measured and calculated half-widths is −2.38 for N2-broadening and −0.65 for air-broadening. The temperature, vibrational, and rotational state dependence of the half-width are investigated. [Copyright &y& Elsevier]

Abstract: Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the ν 4 band of 12CH4 over the temperature range 210–314K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006–0.01cm−1) absorption spectra of pure methane and mixtures of methane diluted with dry air. Line mixing was detected for pairs of A-, E-, and F-species transitions in the P- and R-branch manifolds and quantified using the off-diagonal relaxation matrix elements formalism. The measured parameters are compared to air- and N2-broadened values reported in the literature for the ν 4 and other bands. The dependence of the various spectral line parameters upon the tetrahedral symmetry species and rotational quantum numbers of the transitions is discussed. All data used in the present work were recorded using the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. [Copyright &y& Elsevier]

Abstract: A new spectroscopic experiment has been constructed at the Jet Propulsion Laboratory. This experiment employs the collisional cooling technique to study gases at temperatures below their condensation points. Specifically, the experiment has been designed to mimic the temperatures of the interstellar medium for the study of water under these conditions. The ultimate purpose is to measure state-to-state excitation rates under equilibrium conditions to provide insights into the interpretation of interstellar water spectra obtained from space-borne platforms such as the Herschel Space Observatory. This paper presents an overview of the new experiment including a discussion of its design and a detailed explanation of the system. In addition, we report a pressure broadening study of the J=5←4 transition of CO at 576GHz used as a system validation. The new results are compared with measurements from the literature as a validation of the new experiment. In addition, the non-classical behavior of the pressure broadening of CO at low temperature observed in the measurements will be discussed. [Copyright &y& Elsevier]

Abstract: The self-, nitrogen- and oxygen-broadening parameters of pure rotational water lines in the 1.0–1.2THz frequency range have been measured by means of a frequency modulated spectrometer. The (1.097THz), (1.153THz), (1.158THz), and (1.163THz) transitions have been considered. The experimental determination has been supplemented by theoretical calculations within the semiclassical approximation. [Copyright &y& Elsevier]

Abstract: An investigation of the 110←101 rotational transition of water at 556GHz pressure broadened by hydrogen, helium, nitrogen, oxygen and carbon dioxide has been completed. Using the collisional cooling technique the broadening of this transition by each gas was explored from 200K down to the condensation point of the broadening gas or 17K, which ever is lower. This marks the first time such an extensive investigation of the broadening of this rotational transition as a function of temperature has been completed. The results of this investigation will be presented including the exponential temperature dependence of the broadening, the lack of temperature dependence of the broadening observed in helium and the unique behavior of the hydrogen broadening at low temperature (<40K). In addition, the broadening of the 110←101 rotational transition of water by nitrogen and oxygen was recorded at room temperature and a direct comparison of this data with recent work will be discussed. [Copyright &y& Elsevier]

Abstract: Hydrogen is an important source material in the chemical industry and plays an important role in peripheral and regenerative energy supply like e.g. fuel cells. In particular for hydrogen electrolysis the oxygen concentration is a crucial parameter in respect of the quality of the produced hydrogen and safety aspects. Here we present a spectroscopic sensor, which is appropriate for online-monitoring of oxygen at high pressures. It shows no cross-sensitivities to water and hydrogen, and its optical power is well below the limit of explosion. [Copyright &y& Elsevier]

Abstract: Tuneable diode laser absorption spectroscopy has been used to measure the room temperature pressure broadening coefficients (γ) of rotational transitions in the v 5 fundamental band of methyl bromide (12CH3 79Br and 12CH3 81Br) around 6.9μm. Nitrogen, oxygen and self-broadening coefficients have been determined for 125 lines in the RQ 1, PQ 3, PQ 5, PQ 7 and PQ 8 branches and 49 P and R branch transitions. Line profiles within Q branches were recorded at incremental pressures of nitrogen and oxygen up to 15Torr and fitted to a Voigt profile to yield the broadening coefficients. The nitrogen broadened data for 14 lines, chosen from the five Q branches, were also fitted with Galatry profiles. The line profiles of the P and R branch transitions were recorded for total nitrogen and oxygen pressures of up to 300Torr and fitted to both Voigt and Galatry profiles. Within individual Q branches, nitrogen broadening coefficients were found to decrease monotonically with increasing J from 0.14cm−1 atm−1 at low J to 0.09cm−1 atm−1 at high J. The corresponding values for oxygen were approximately 25% smaller. Self-broadening coefficients were found to vary between 0.48 and 0.16cm−1 atm−1 with a similar J dependence to the foreign gas broadening for J >20. However, between J =2 and J ≈20 the broadening coefficient was found to increase with J. The magnitude of the pressure broadening coefficient for P and R branch transitions was found to closely follow the J dependence measured for the Q branch lines. [Copyright &y& Elsevier]

A physical model is established to describe the broadening mechanism of rubidium atomic D1 and D2 lines, hence to improve rubidium vapor laser efficiency. Hyperfine energy level structures of rubidium D1 and D2 transitions are analyzed and plotted. Considering the effects of the isotopic frequency shift, the pressure broadening and the hyperfine energy levels splitting, contributions of every hyperfine component to the cross sections are calculated and discussed. The relationship between cross sections and the ratio of helium pressure to ethane is achieved, and the composition of the buffer gas is optimized. The broadening effects of Rb D1 line and D2 line under different buffer gas pressure are also presented. The calculation results have a good agreement with that of experiments, which shows the validity of this model. The simulations data provides a reference for the experiment to further improve the bandwidth matching between alkali atomic D2 absorption line and the diode laser pump source. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spectral features and dynamics of 12CH 2 D 2 isotopomer has been explored using high-resolution CRDS technique. • Theoretical simulations using Gaussian 16 and PGOPHER have been performed. • Spectroscopic parameters like absorption cross-section, pressure broadening co-efficient have been calculated using various perturbing gases. • Dependency of pressure broadening coefficient on the rotational quantum number (J) have been analysed. • Our highly sensitive spectroscopic study will help for the better understanding of detailed structural dynamics of 12CH 2 D 2. Dideutero-methane 12CH 2 D 2 is unique among all the methane isotopomers because of its asymmetric-top nature. Here, we first report the fine ro-vibrational gas-phase spectra of 12CH 2 D 2 isotopomer in the a -type ν 9 (B 2 -symmetry) fundamental band near 7.8 µm using ultra-sensitive cavity ring-down spectroscopy (CRDS) instrument in the mid-infrared spectral region. We utilized Gaussian 16 to calculate the relevant spectroscopic parameters of 12CH 2 D 2 and subsequently performed the PGOPHER simulation for precise assignments of the fine ro-vibrational lines of 12CH 2 D 2. Further, we conducted the pressure broadening dynamics of 12CH 2 D 2 isotopomer with various foreign gases and accurately determined the pressure broadening coefficients, γ i in cm−1 atm−1 [ i = He, Ar, N 2 , Hydrogen mixture(H 2 + N 2) and zero air] of various transition lines of 12CH 2 D 2. [ABSTRACT FROM AUTHOR]

Directly rapid depressurization foaming process has been successfully applied to prepare microcellular epoxy foams using supercritical CO 2 as blowing agent. It is found that both curing reaction and CO 2 diffusion are crucial for controlling cell morphology. For epoxy of tetraglycidyl-4,4′-diaminodiphenyl-methane (TGDDM) and 4,4-diaminodiphenylsulfone (4,4-DDS) system, the experimental and molecular simulation results displayed that higher CO 2 pressure always promotes curing reaction, and CO 2 diffusion is more sensitive to pressure at low curing degree, while limited by high curing degree. The foaming experimental results showed that there existed a suitable curing degree range, in which both unsaturated CO 2 concentration and curing degree contribute to good cell structure. Higher CO 2 pressure can broaden this foamable window. The microcellular epoxy foam with an average cell diameter of 14.6 µm and cell density over 109 cells/cm3 as well as volume expansion ratio of 14.5 has been obtained at 85% curing degree under 22 MPa CO 2 pressure. [Display omitted] • Microcellular epoxy with expansion ratio over 10 has been successfully foamed by supercritical CO 2. • Higher CO 2 pressure always promotes curing reaction. • CO 2 diffusion was more sensitive to pressure at low curing degree, while limited by high curing degree. • Both curing degree and CO 2 concentration contribute to good cell structure. [ABSTRACT FROM AUTHOR]

• Non-Markov perturbation approach to the rotational relaxation matrix. • Formation of satellites in the far wings of allowed IR and Raman lines. • Collision-induced intensity transfer from the peaks of allowed lines to the wings. A non-Markov theory of diffuse satellites developing around the allowed (mother) rotational lines perturbed by monoatomic buffer gases is expounded. As the buffer-gas pressure grows, the lorentzian part of mother lines adjacent to the band origin becomes attenuated because of the intensity transfer to pressure-enhanced satellites. Different channels contributing to the attenuation of infrared and Raman lines of linear molecules are considered. Simple estimations of the attenuation coefficients reasonably fit experimental data available for the HCl and HF absorption spectra perturbed by monatomic gases. [ABSTRACT FROM AUTHOR]

Abstract: The classical theory of collisional broadening and shift parameters (β, δ) of an isolated spectral line was used to obtain simple analytical formulas for calculating both β and δ. These formulas were obtained on the assumption that the short range interaction is effective only in the broadening while the long range is effective in the shift of the spectral line. These parameters β and δ depend on the limiting phase shifts responsible for broadening η b and shift ηδ. It was found that the values of η b and ηδ are not equal to each other as was proposed by Weisskopf η b=ηδ =1. The maximum and average values of η b (η bmax, η bav) and ηδ (ηδ max, ηδ av) were obtained by numerical evaluation, using different inverse power potentials. By introducing these parameters into the approximated formulas for β and δ using Van der Waals and Lennard-Jones potential, it was found that the results of calculations for (β and δ) with different atomic transitions perturbed by different inert gases are in close agreement with earlier results. Those results, obtained earlier, were based on the Lindholm–Foley theory especially with the average values of η b [η bav=0.6057] and the maximum values of ηδ [ηδ max=1.57625]. The impact parameters ρ b and ρδ leading to the broadening and shift of the spectral line were also obtained for different interactions. It was found that the end parameter for the broadening ρ b is not equal to the starting parameter for the shift ρδ . [Copyright &y& Elsevier]

The challenge of wellbore stability is getting harder in complex formations. A better understanding of mud cake and its effect on stress state around the wellbore is beneficial for the solution of wellbore stability problems. Thus, the testing method and describing function of dynamic mud cake properties were developed with different drilling fluid additives. The microstructure of mud cake was investigated to further illustrate the mechanism of drilling fluid additives. Based on the poroelastic model, the effect of time-dependent mud cake properties on the distribution of pore pressure, effective stress state around the wellbore and safe mud weight window was analyzed. The results indicate that the buildup of mud cake slows down the increase of pore pressure and broadens the safe mud weight window by increasing the effective stress of compression. The significant increase in fracturing pressure illustrates the potential effect of mud cake in wellbore strengthening. Although the pressure isolation effect increases with the addition of bentonite, it has a limited influence on the safe mud weight window. The addition of Xanthan (XC) enhances the pressure isolation effect of mud cake by improving the coalescence stability of fine-grained particles and plugging the pore with hydration membrane. The viscoelastic granular plugging material has the best sealing efficiency with the deformation property. Although the fine-grained walnut shell has a relatively good pressure isolation effect, its effect on borehole cleaning is far greater than that on wellbore stability. • The testing method and descriptive function of dynamic mud cake properties were developed. • A hydro-mechanical model was developed with the effect of time-dependent mud cake. • The combination of bentonite, polymer and viscoelastic plugging material had the best pressure isolation effect. The addition of plugging material decreases the pore pressure, which indicates that the pressure isolation effect of mud cake can be effectively improved with the packing of rigid particles (Fig. 20). When the content of plugging material is high, the pore pressure decreases slightly, which illustrates that the increase of rigid materials cannot obviously enhance the compactness of the plugging zone. The addition of plugging material increases the effective stress of compression, which shows that the plugging of rigid particles decreases the risk of wellbore instability with higher compressive strength. [ABSTRACT FROM AUTHOR]

• SPEARS allows for simultaneous synthesizing of multiple spectroscopic databases. • Physics-based approach for modeling pressure broadening effects on spectra. • Adaptive grid mesh algorithm allows for fast simulation of spectra at high fidelity. The Spectral Physics Environment for Advanced Remote Sensing (SPEARS) application programming interface (API) is a Python-based, line-by-line, local thermal equilibrium (LTE) spectral modeling code which is optimized for simultaneously synthesizing optical spectra from any combination of fundamental spectroscopic databases. In this article, we contribute two novel spectral modeling techniques to the scientific literature. First we describe how SPEARS integrates a physics-based collisional model for calculating pressure broadening in the absence of available broadening coefficients. With this collisional model implementation, a generalized approach to fundamental spectroscopic databases can be achieved across multiple databases. We also detail our adaptive grid mesh algorithm developed to make the code scalable for simulating large spectral bandwidths at high spectral fidelity using intuitive grid parameters. We present comparisons to other modeling tools, experiments, and provide a discussion on the SPEARS user interface. [ABSTRACT FROM AUTHOR]

Abstract: We present experimental data on the previously unknown line broadening and shifting coefficients in the (2←0) overtone vibration–rotation bands of the HBr and HI molecules in mixtures with several rare gases. The vibrational dependence of the isotropic and anisotropic components of the binary interaction potential is probed by separating the measured line shifts into parts symmetric and asymmetric in the line number m and by comparing with the previously published similar data for the fundamental bands of the same molecules. It is shown that the line shifts are dominated by the vibrational dependence of the isotropic potential. A linear correlation is found between the asymptotic values of the symmetric shifts in the overtone bands for all HX–Rg (X=F, Cl, Br, I) pairs and the respective C6 long-range potential energy constants. Line broadening parameters in the overtone band of pure HBr are also reported. [Copyright &y& Elsevier]

Abstract: The aim of this work is to determine quantum mechanically the width and the shift of the lithium and potassium resonance lines when these atoms are evolving in their parent gases. The interaction potentials along which the atoms and approach each other are constructed from reliable data. The radial wave equation is then solved numerically by using these potentials to compute the elastic phase shifts. By adopting the simplified Baranger model for the pressure broadening, which assumes the impact approximation, the cross sections effective in linewidth and lineshift are analyzed. The analysis leads in particular to the determination of the width and shift rates and the computations show that these rates have constant values and, mainly, do not depend on temperature. An approximate method is further applied to the calculations of the cross sections. The results reveal the influence of the long-range interactions and confirm the universality of the obtained formulas of and . [Copyright &y& Elsevier]

Abstract: Broadening and shifting of carbonyl sulfide (OCS) rotational spectrum lines by pressure of N2, O2 and OCS were accurately studied in the frequency range 24–850GHz at room temperature using a spectrometer with radio-acoustic detection of absorption. Rotational dependences of collisional widths of OCS spectrum lines were determined by a simple empirical polynomial fit of experimental data. Experimental uncertainties were analyzed. Results of supplementary test measurements of self-broadening of rotational OCS lines in the ν 2 excited vibrational state and carbon monoxide (CO) lines in the ground vibrational state are presented. Comparison of the obtained results with previously known measurements and theoretical calculations is given. The performed work allows for the first time development of accurate gaseous etalon of absorption for atmospheric applications and laboratory use, covering continuously the whole millimeter- and submillimeter-wave range. [Copyright &y& Elsevier]

• Development of a temperature-dependent line mixing model for nitric oxide near 5.2 μ m broadened by N 2 and Ar through energy gap fitting laws applied to experimental pressure broadening coefficients. • High-pressure (up to 33 atm) and high-temperature (up to 802 K) measurements of the nitric oxide R-branch in N 2 compare favorably to the line mixing model. • The nitric oxide line mixing model is applied to a two-wavelength temperature measurement strategy in high-pressure shock tube experiments at pressures up to 90 atm and temperatures up to 2500 K with relatively good agreement between measured and known temperatures. Evidence of line mixing has been observed in the infrared spectra of many gaseous species at high densities or in the low absorbing windows between optical transitions. However, up to this point, no study exists of nitric oxide line mixing at pressures above atmosphere or temperatures several hundred degrees above room temperature. In this paper, the absorption spectrum of nitric oxide's R-branch broadened by N 2 near 5.2 microns is measured with an external cavity quantum cascade laser in a high-pressure, high-temperature optical static cell over a range of temperatures (294 – 802 K) and pressures (5 – 33 atm). An empirically-based, temperature-dependent line mixing model is built by assembling the impact relaxation matrix from fits (energy gap fitting laws) to pressure broadening coefficients that were measured in a previous study. The resulting line mixing model shows significant improvements over a simple superposition of Lorentzian line shapes when compared to the static cell measurements. To further demonstrate the model's use, the line mixing model is used to infer temperature in high-pressure (10 – 90 atm) shock tube experiments. [ABSTRACT FROM AUTHOR]

• Comprehensive dataset of beyond-Voigt line-shape parameters for He-perturbed HD. • Ab initio quantum scattering calculations of generalized spectroscopic cross-sections. • Ab initio investigation of pressure broadening, shift and Dicke parameters. • Data for all electric dipole and quadrupole lines that are present in HITRAN database. We report a comprehensive dataset of beyond-Voigt line-shape parameters (pressure broadening and shift coefficients, their speed-dependences, and the complex Dicke parameters) for all electric dipole and quadrupole transitions within the ground electronic state in He-perturbed HD that are present in the HITRAN database. The parameters are determined from generalized spectroscopic cross-sections which we obtain by solving ab initio quantum scattering problem using the close-coupling formulation and the state-of-the-art potential energy surface of the HD-He interaction. We parametrize the temperature dependence of the line-shape parameters with double-power-law representation (DPL), recommended for the HITRAN database. Comparison with the analogous results for the H 2 -He system reveals a strong isotopologue dependence. [ABSTRACT FROM AUTHOR]

• Broadband, high-resolution dual frequency comb absorption spectroscopy of pure CO 2 between 6800 – 7000 cm-1 at temperatures up to 981 K. • Temperature-dependent line shape parameters measured for more than 110 transitions in the 00031←00001 and 01131←01101 bands using multispectrum analysis with both a Voigt and speed-dependent Voigt profile. • Comparison to calculated line shape parameters, including the updated parameter set used in the HITRAN2020 database. • Empirical models for the broadening coefficient, pressure shift coefficient, and their temperature dependence validated for high-temperature transitions up to | m |≈90. We present the first systematic study of self-broadened CO 2 line shape parameters in the 00031 ← 00001 and 01131 ← 01101 bands at high temperature. We report temperature-dependent broadening coefficients and pressure shift coefficients for more than 40 transitions in the 00031 ← 00001 band, and 75 transitions in the 01131 ← 01101 hot band. The majority of these parameters have never been measured at high temperature. The new parameters are determined from 12 spectra measured with a broadband, high-resolution dual frequency comb absorption spectrometer in a high-temperature gas cell from room temperature to 980 K. We fit the measured spectra using a multispectrum fitting approach to derive line shape parameters with both a Voigt and speed-dependent Voigt profile. We compare the measured parameters to calculated line shape parameters as well as to the new parameter set developed for the HITRAN2020 database. The new measurements demonstrate strong agreement with HITRAN2020 (within 1% in some cases), and provide new measurements of the temperature dependence of the broadening and pressure shift coefficient that will improve the accuracy of the database at high temperature. We extend our results to high | m | transitions using a set of empirical models for the broadening and pressure shift coefficients, which we fit to our data and validate for high-temperature transitions up to | m | = 98. We use these models to construct a set of database files that can be used to supplement the HITRAN database for self-broadened CO 2 in the 6800 – 7000 cm-1 region. These new parameters significantly improve the accuracy of absorption models for high-temperature CO 2 in this frequency range, and also provide useful data to test and improve methods used to calculate CO 2 line shape parameters. [ABSTRACT FROM AUTHOR]

Abstract: We have measured the room temperature pressure broadening coefficients, γ, of over 100 lines in five Q-branches of the ν 5 perpendicular band of methyl iodide (12CH3I) using tuneable diode laser absorption spectroscopy. The profiles of individual lines in the PQ2, PQ4, PQ5, PQ6 and RQ3 branches were recorded in a 1m long White cell and at nitrogen or oxygen pressures up to 15Torr. The lines were fitted to the Voigt profile to obtain the collision broadened line widths. Within individual Q-branches the broadening coefficients decreased monotonically with increasing J and for nitrogen broadening varied between 0.19cm−1 atm−1 at low J and 0.12cm−1 atm−1 at high J. The corresponding oxygen broadening coefficients were approximately 20% smaller. Self broadening coefficients were also measured for several of the Q-branches and found to be up to ∼4 times higher than the corresponding nitrogen broadening values. [Copyright &y& Elsevier]

A continuous wave cavity ring-down (cw-CRD) spectrometer has been developed for the measurement of trace levels of water vapor by absorption spectroscopy at wavelengths in the vicinity of 1358 nm and 1392 nm. The speed of data acquisition and selectivity make cavity ringdown spectroscopy potentially more useful than current techniques for measurement of trace water in process gases and vacuum environments used for semiconductor manufacture where water vapor contamination has a detrimental effect on the final product. The pressure broadening coefficients (γ) for bath gases N2, air, and Ar and semiconductor process gases SiH4, PH3, and CF4 were determined for a range of absorption lines in the 2ν1 and ν1 + ν3 bands of H2O. For the transitions investigated, the concentration of water vapor in the sample gas varied from 1.7 × 1012 to 2.9 × 1015 molecule cm−3 in N2 at a total pressure of <10 mbar and was mixed with the bath gas of increasing pressure up to ∼200 mbar. The values of γ quantify the reduction in peak absorption cross-sections with bath gas pressure and, thus, their effects on the detection limit of water vapor. For a CRD spectrometer with a ring-down time of τ = 12.0 μs measured with a precision of 0.6%, detection limits for the measurement of water vapor in 1 atm N2 and of CF4 were estimated to be 18 and 14 ppbv, respectively. Competing absorption by SiH4 and PH3 in the 1.3 μm wavelength region results in respective detection limits for water vapor of 98 and 319 ppbv (relative to 1 atm) in 0.2 atm SiH4 and 0.37 atm PH3. [ABSTRACT FROM AUTHOR]

Abstract: The self-, nitrogen- and oxygen-broadening of the (1.147THz), (1.168THz), (1.173THz), (1.191THz), and (1.542THz) rotational transitions of water vapor have been experimentally and theoretically investigated in the present work, showing that the corresponding HITRAN self-broadening parameters are affected by large errors. Indeed, simple semiclassical calculations performed for more than 1500 rotational water lines with wavenumber below allow us to improve the self-broadening values reported in the HITRAN database when obtained by assuming a J dependence. On the other hand, our measurements and calculations confirm the values reported in the HITRAN database for air-broadening and shift, which are based on semiclassical computations as well. On the whole, the present investigation provides new experimental as well as theoretically improved values for self-broadening parameters of rotational lines in the THz frequency region. [Copyright &y& Elsevier]

Abstract: Using a high-resolution tunable diode laser photoacoustic spectrometer, self-, N2 and O2 pressure broadening coefficients for the first 11 transitions of 12C16O2 in the R branch of the (30012)←(00001) overtone band at the 6348cm−1 have been revisited at room temperature (∼298K). Air-broadening parameters have also been calculated from the N2 and O2 measurements. The dependence of the broadening on rotational quantum number m is discussed. The recorded lineshapes are fitted with standard Voigt line profiles in order to determine the collisional broadening coefficients of carbon dioxide transitions. The results are compared to our previous measurements and to the values reported in the HITRAN04 database and by other research group with a different spectroscopic technique. [Copyright &y& Elsevier]

Abstract: Water vapor infrared spectra have been measured using the Bruker IFS 120 HR Fourier transform spectrometer at the Physikalisch-Chemisches Institut of the Justus-Liebig-Universität Giessen. Spectra were recorded at pressure-broadening-limited resolution and at room temperature in the range of 1900–6600cm−1. The use of fully evacuated transfer optics and a White-type multireflection cell made it possible to obtain pressure×pathlength products up to 31.27mbar×288.5m. These spectra have previously been used to determine experimental values of rovibrational line positions and upper energy levels of the 2ν 2, ν 1, and ν 3 bands [Mikhailenko SN, Tyuterev VlG, Keppler KA, Winnewisser BP, Winnewisser M, Mellau G, et. al. The 2ν 2 band of water: analysis of new FTS measurements and high-Ka transitions and energy levels. J Mol Spectrosc 1997;184: 330–49] and of the 3ν 2, ν 1+ν 2, and ν 2+ν 3 bands [Mikhailenko SN, Tyuterev VlG, Starikov VI, Albert KK, Winnewisser BP, Winnewisser M, et al. Water spectra in the region 4200–6250cm−1, extended analysis of ν 1+ν 2, ν 2+ν 3, and 3ν 2 bands and confirmation of highly excited states from flame spectra and from atmospheric long-path observations. J. Mol. Spectrosc. 2002; 213: 91–121]. This work presents the intensities of 3769 lines for the weak and medium transitions in the spectral range indicated. These data provide an independent source of experimental information which is complementary to intensity data available in the literature and can thus help to evaluate experimental errors and the reliability of these spectral line parameters. [Copyright &y& Elsevier]

Abstract: The absorption spectrum of H2O has been extensively studied over the past decades in the near-infrared and visible regions, but there remain significant discrepancies in the 10,000–12,500cm−1 range even for the most intense lines. We have studied 24 lines of H2O using an external-cavity diode laser emitting in the 810–830nm range, in order to measure absolute line intensities as well as air- and self-broadening coefficients. Comparisons were made with values obtained from the HITRAN database and also with other parameters from recent experiments or predicted calculations. It is suggested that neglecting the effects of H2O collisional narrowing in radiative transfer calculations of the Earth''s atmosphere may have a small but significant impact on the radiative budget of the Earth. [Copyright &y& Elsevier]

Abstract: Pressure broadened (1atm. N2) laboratory spectra of benzene vapor (in natural abundance) were recorded at 278, 298, and 323K, covering 600–6500cm−1. The spectra were recorded at a resolution of 0.112cm−1 using a commercial Fourier transform spectrometer. The pressure of each benzene vapor sample was measured using high-precision capacitance manometers, and a minimum of nine sample pressures were recorded for each temperature. The samples were introduced into a temperature-stabilized static cell (19.94(1)cm pathlength) that was hard-mounted into the spectrometer. From these data a fit composite spectrum was calculated for each temperature. The number density for the three composite spectra was normalized to 296K. The spectra give the absorption coefficient (cm2 molecule−1, naperian units) as a function of wavenumber. From these spectra integrated band intensities (cmmolecule−1 and atm−1 cm−2) for intervals corresponding to the stronger benzene bands were calculated and were compared with previously reported values. We discuss and quantify error sources and estimate our systematic (NIST Type-B) errors to be 3% for the stronger bands. The measured absorption coefficients and integrated band intensities are useful for remote sensing applications such as measurements of planetary atmospheres and assessment of the environmental impact of terrestrial oil fire emissions. [Copyright &y& Elsevier]

Abstract: The absorption spectrum of SO2 has been studied with 2MHz instrumental resolution in the wavenumber range , using a difference frequency spectrometer based on diode lasers for the 1300 and 1550nm telecom bands. Initially, Lorentz broadening parameters are determined, at pressures up to 400Pa, for 545 lines covering lower state J up to 60 and up to 14. Using this information in conjunction with spectra recorded at 100 and 200Pa the line strength is subsequently determined for 395 lines of the band of 32SO2, 170 lines from the hot band of 32SO2, and 98 lines from the band of 34SO2, and dipole moments are derived for all three bands. For the hot band, line positions of 178 transitions are measured and merged with previously published data to produce an improved set of Hamiltonian parameters for the state, using the most recent model for . [Copyright &y& Elsevier]

Abstract: Experimental and theoretical investigations of ozone lines broadened by nitrogen as well as oxygen have been carried out in the 300–320GHz frequency range. Lineshape analysis has demonstrated clear departures from the usual Voigt profile, actual lineshapes being narrower and higher than expected. More refined models, such as the Galatry and speed-dependent Voigt profiles, have been used. Both of them have been found to reproduce the experimental lineshapes well. However, while for the latter, the narrowing parameter shows a linear behavior with pressure, for the Galatry profile a strong nonlinear behavior is observed. Such observations demonstrate that the Dicke narrowing effect, related to molecular diffusion, cannot be the leading process involved. Experimental results have also been compared to the theoretical ones. The relaxation rate dependence on molecular speed has been computed employing the Robert–Bonamy semiclassical theory. These calculations confirm the leading role of molecular speed dependence effects. Finally, it is inferred that optical diffusion rates are much lower than the kinetic diffusion rate, a conclusion well supported from the comparison of optical and Lennard–Jones radii. [Copyright &y& Elsevier]

Abstract: The temperature dependence of the Cd line absorption profile at 326.1nm perturbed by Kr has been carefully studied over a spectral range extending from 800cm−1 in the blue wing to 1200cm−1 in the red wing using a high-resolution double-beam spectrometer. The atomic densities of krypton (N Kr) and cadmium (N Cd) were (2.015±0.07)×1019 and (3.62±0.05)×1018 cm−3, respectively. The temperature dependence of the studied line profile was analyzed in the framework of the quasi-static theory. The van der Waals coefficient differences between the ground 10+ state and the two excited states 30+ and 31 (ΔC 6 0 and ΔC 6 1) were obtained from the near red wing profile using Kuhn''s law. The values of ΔC 6 0 and ΔC 6 1 are found to be equal to 37.8±2 and 58.5±3eVÅ6, respectively. The ground (X 10+), and the excited (31, 30+) state potentials at the internuclear separations from 3.2 to 6.3Å were determined. The well depths with their positions for these states are respectively equal to 134±7cm−1, 3.95±0.2Å; 72.3±4cm−1, 4.95±0.3Å; and 471±12cm−1, 3.6Å. The obtained well depths with their allowable errors are in good agreement with the values obtained before for the Cd–Kr system from some theoretical results and molecular beams experiments. [Copyright &y& Elsevier]

Abstract: This paper is devoted to the measurement of pressure shift and broadening parameters of water-vapor lines of the pure rotational transition 110–101 in the ground vibrational state of H2 16O at 556.936GHz, H2 17O at 552.02GHz, H2 18O at 547.676GHz, and the vibrationally excited state v 2=1 line of H2 16O at 658.003GHz. The broadening coefficients of the line at 556.936GHz (for N2 and O2 as perturbing gases) coincide within the errors with the values obtained recently by Seta et al. [Pressure broadening coefficients of the water vapor lines at 556.936 and 752.033GHz. JQSRT 2008;109:144–50] by means of a very different technique (THz-TDS). Pressure shift and broadening for other lines were measured for the first time. Comparison of our results with previous measurements and theoretical calculations is presented. [Copyright &y& Elsevier]

Abstract: The dependence of pressure broadening upon hyperfine component in the P(10) and P(70) lines of the (17,1) band of the I 2 X1Σ(0g +)→B3Π(0u +) has been studied using laser saturation spectroscopy. By limiting absorption to the zero velocity group, Doppler broadening is removed, lineshapes with widths (FWHM) <9MHz are detectable, and collision-induced broadening is measured at pressures of 0.2–1.2Torr. The rates for broadening by argon are 8.3±0.3 and 10.7±0.4MHz/Torr for the P(70) and P(10) lines, respectively. No significant variation in broadening rates is observed for the 15 hyperfine components of these even rotational lines. The effects of velocity cross-relaxation introduce a broad baseline into the spectra, which is strongly dependent on rotational state, pressure, and laser modulation frequency. The observed broadening rates correlate well with prior measurements and the polarizability of the collision partner. [Copyright &y& Elsevier]

Abstract: We report N2 and air foreign pressure broadening coefficients of more than twenty rovibrational transitions of water vapor in the 935-nm spectral region, and these measurements are compared to new theoretical calculations. The data were obtained using the frequency-stabilized cavity ring-down spectroscopy method, yielding relative uncertainties for the broadening parameters in the range 0.4–2.2%. The sensitivity of measured broadening parameters to the choice of line shape functions is discussed, and systematic differences between experimentally determined collisional broadening coefficients are shown for the cases when the observed line narrowing is interpreted in terms of Dicke-narrowing or the speed-dependence of the collisional broadening and shifting. Theoretical models of pressure broadening for these transitions agree with the measurements to within 4% for most transitions with an average relative difference of 0.63%. [Copyright &y& Elsevier]

Abstract: A multispectrum nonlinear least-squares fitting technique was applied to measure accurate zero-pressure line center positions, Lorentz self- and nitrogen (N2)-broadened half-width coefficients, and self- and N2-pressure-induced shift coefficients for over 700 transitions in the parallel ν 4 band of CH3CN near 920cm−1. Fifteen high-resolution (0.0016cm−1) laboratory absorption spectra of pure and N2-broadened CH3CN recorded at room temperature using the Bruker IFS 125HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, USA, were analyzed simultaneously assuming standard Voigt line shapes. Short spectral intervals containing manifolds of transitions from the same value of J were fitted together. In all, high-precision line parameters were obtained for P(44)–P(3) and R(0)–R(46) manifolds. As part of the analysis, quantum assignments were extended, and the total internal partition function sum was calculated for four isotopologs: 12CH3 12CN, 13CH3 12CN, 12CH3 13CN, and 13CH3 13CN. Measurements of N2 broadening, self-broadening, N2-shift, and self-shift coefficients for transitions with J up to 48 and K up to 12 were measured for the first time in the mid-infrared. Self-broadened half-width coefficients were found to be very large (up to ∼2cm−1 atm−1 at 296K). Ratios of self-broadened half-width coefficients to N2-broadened half-width coefficients show a compact distribution with rotational quantum number in both the P and R branches that range from ∼4.5 to 14 with maxima near ∣m∣=24, where m=−J″, J″, and J″+1 for P, Q, and R lines, respectively. Pressure-induced shifts for N2 are small (few exceed ±0.006cm−1 atm−1 at 294K) and are both positive and negative. In contrast, self-shift coefficients are large (maxima of about ±0.08cm−1 atm−1 at 294K) and are both positive and negative as a function of rotational quantum numbers. The present measured half-widths and pressure shifts in ν 4 were compared with corresponding measurements of rotational transitions. [Copyright &y& Elsevier]

Pressure broadening and shift coefficients for the ν1+ν3 band of 12C2H2 have been measured for He, Ne, and Ar at a temperature of 195 K using high resolution diode laser spectroscopy. The pressure broadening and shifts follow patterns with rotational assignment that are similar to those at room temperature but are generally larger in magnitude. The change in magnitude is qualitatively described by assuming, for each transition, a constant cross section for pressure broadening or shifting. Better agreement may be obtained for pressure broadening coefficients by using empirically determined temperature exponents; better agreement still is obtained from close coupling calculations of the pressure broadening cross sections. [ABSTRACT FROM AUTHOR]

Abstract: The air induced broadening coefficients of the pure rotational transitions of HO at 556.936GHz , and 752.033GHz were measured by terahertz time-domain spectroscopy. The air broadening coefficient was determined to be for the 556.936GHz line and for the 752.033GHz line, respectively. The present broadening coefficients for the 556.936 GHz water line are significantly smaller than those of Markov and Krupnov [Measurements of the pressure shift of the 1(10)–1(01) water line at 556.936GHz produced by mixtures of gases. J Mol Spect 1995:172;211–4] but relatively close to the values of the HITRAN database. The measured data may improve the accuracy of the abundance of water vapor retrieved from spectra obtained by the Odin/SMR satellite instrument. The effect on the satellite retrieval processing is discussed. [Copyright &y& Elsevier]

Abstract: Experimental lineshapes of the 172 and 602GHz millimeter lines of HC15N in collision with H2, N2, O2, CH3CN and some rare gases are studied for the purpose of atmospheric applications and detailed collision analysis. Using of a sensitive frequency modulation technique allows highlighting clear deviations from the usual Voigt profile, these departures being generally considered as related to molecular diffusion effects or to the dependence of collisional relaxation rates on molecular speeds. Except the light buffer gases H2 and He, the linefits using the Galatry profile lead to nonlinear pressure dependencies of relaxation rates, that rules out the frequent hypothesis of an exclusive role of molecular diffusion (Dicke effect). This observation is shown to be in accordance with the fact that optical radii related to relaxation are usually greater than kinetic Lennard-Jones radii tied to diffusion. In contrast, the actual lineshapes are well reproduced by the Speed-Dependent Voigt profile taking into account the speed dependence of relaxation rates which display linear pressure dependencies. For the particular cases of the N2- and Ar-HCN pairs, the experimental results are rather well explained by semi-classical computations based on the Robert–Bonamy formalism improved by the model of exact trajectories. These computations show that relaxation rates are proportional to some power of the colliders’ relative speed. A detailed comparison of relaxation parameters deduced from low-pressure experiments with Galatry and Speed-Dependent Voigt profiles allows to infer that the optical diffusion rates are much smaller that kinetic ones, so that the experimental lineshapes depend nearly exclusively on the speed dependence of relaxation rates and are weakly affected by molecular diffusion effects. Extension of these conclusions to other molecules of atmospheric interest is discussed. Finally, an appendix presents unpublished results dealing with the collisional relaxation of some rotational lines of HC15N (at 258GHz for different temperatures and at 344GHz) and HC14N (at 355GHz). [Copyright &y& Elsevier]

Abstract: CARS laboratory experiments were done in the 2905–2925cm−1 range, in the vicinity of the ν 1 band of the methane molecule, for pressures ranging from 1 to 50 bar, and temperatures up to 1100K. These experiments were carried out in order to retrieve the pressure evolution of the CH4 spectrum, as well as to confirm its temperature dependance. After a brief recall on the theory used to compute pressure broadening coefficients and relaxation rates, we consider the ν 3 and ν 4 infrared bands of methane for benchmark calculations purposes. Next, we present recent experimental CARS spectra and calculated ones. Lastly, we discuss flame experiments as well as comparisons of temperature retrieval using N2 and CH4 as probe molecules. [Copyright &y& Elsevier]

Abstract: We present measurements of He-broadening parameters for the R(0) and P(2) lines in the fundamental band of 13CO at different temperatures between 12K and room temperature. The broadening parameters are determined, taking into account confinement narrowing, by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The pressure broadening cross sections are deduced and compared to close-coupling calculations and earlier results obtained for rotational transitions of 12CO. [Copyright &y& Elsevier]

Abstract: The temperature dependent pressure induced broadening of several oxygen resonant transitions have been measured. For the isolated magnetic fine-structure transition and the magnetic rotational transition are investigated in both nitrogen and oxygen. Additionally, pressure broadening of the magnetic rotational transition of 18O16O is measured in air. This work improves precision and accuracy of the linewidth of the fine-structure transition and provides the first temperature dependent linewidth measurements at higher frequency. [Copyright &y& Elsevier]